1. Field of the Invention
The present invention relates to an apparatus in connection with a derrick, comprising two or more hydraulic piston/cylinder arrangements for raising and lowering a yoke which travels on guide rails in the derrick itself.
2. Description of the Related Art Including Information Disclosed Under 37 C.F.R. .sctn. .sctn. 1.97 and 1.98
A derrick structure, developed by the present inventor in 1987, that has shown great promise is the RamRig.TM. concept. Two hydraulic piston/cylinder arrangements are used in the derrick for raising and lowering the drill string. The cylinders operate between the drill floor and a yoke which travels on guide rails in the derrick itself. The advantages of this concept are numerous, some of the most important being that it is possible to place the drill floor at a higher level than the platform floor, that a derrick having significantly lower air resistance can be constructed, and that the most expensive components of the derrick attain higher safety and a longer lifetime.
Since it is possible to position the drill floor higher than the platform floor, pipe handling is significantly simplified. There is no longer any need to arrange the pipe handling equipment at a high level in the derrick. All pipe handling equipment can be placed on the platform floor and the drill floor.